Mark, method for forming same, and exposure apparatus

ABSTRACT

A mark forming method includes: forming recessed portion on a mark formation area of a substrate; coating the recessed portion with a polymer layer containing a block copolymer, allowing the polymer layer in the recessed portion to form a self-assembled area; selectively removing a portion of the self-assembled area; and forming a positioning mark by using the self-assembled area from which the portion thereof has been removed.

CROSS REFERENCE TO RELATED APPLICATION

This application is a Continuation of application Ser. No. 14/590,376,filed on Jan. 6, 2015, which is a continuation application ofInternational Patent Application No. PCT/JP2013/068752 entitled MARK,METHOD FOR FORMING SAME, AND EXPOSURE APPARATUS” and claiming thebenefit of priority of Japanese Patent Application No. 2012-154373 filedon Jul. 10, 2012. The disclosures of the prior applications areincorporated herein by reference in their entireties.

TECHNICAL FIELD

The present invention relates to a mark formed in a mark formation areaof a substrate, a mark forming method for forming the mark, an exposureapparatus using the mark, and a method for producing device using theexposure apparatus.

BACKGROUND ART

A semiconductor device typically includes a plurality of layers ofcircuit patterns formed on a substrate, and a positioning mark oralignment mark is formed in a mark formation area of a predeterminedlayer of the substrate so as to accurately align the circuit patterns ofthe plurality of layers relative to each other, in a production step ofthe semiconductor device. In a case that the substrate is asemiconductor wafer (hereinafter referred to simply as “wafer”), thealignment mark is referred to also as a “wafer mark”.

Conventionally, the minutest circuit pattern of the semiconductor deviceis formed, for example, with a dry or liquid immersion lithography stepusing a dry or liquid immersion exposure apparatus of which exposurewavelength is 193 nm. It is expected that formation of a circuit patternmore minute, for example, than a 22 mm node is difficult even bycombining the conventional photolithography and the double-patterningprocess which has been recently developed.

In view of this situation, it has been suggested using the directedself-assembly (directed self-organization) of a block copolymer betweenpatterns formed by using the lithography step so as to generate a minutestructure of nano-scale (sub-lithography structure), thereby forming acircuit pattern more minute than the resolution limit of the currentlithography technique (see, for example, the specification of U.S.Patent Application Publication No. 2010/0297847 or Japanese PatentApplication Laid-open No. 2010-269304). The patterned structure of theblock copolymer is also known as a micro domain (micro phase-separateddomain) or simply as a domain. The graphoepitaxy is known as a methodfor generating the directed self-assembly.

SUMMARY

It is possible to form a minute circuit pattern of the nano-scale in acertain layer of the substrate by using the directed self-assembly ofthe block copolymer. In some cases, it is further required to form analignment mark in the certain layer, together with the circuit pattern.However, in a case that the alignment mark is merely formed with anyconventional method, any unexpected minute structure is formed also inthe alignment mark itself due to the self-assembly of the blockcopolymer; in such a case, if the alignment mark is hard to be detectedin a step after the formation step, there is a fear that the overlayaccuracy between the layers of the substrate might be lowered.

In view of such a situation, a purpose of an aspect of the presentteaching is to provide a mark forming method which is usable whenforming a circuit pattern by using the self-assembly of the blockcopolymer, and to provide a mark formed by the mark forming method.

According to a first aspect of the present teaching, there is provided amark forming method comprising: forming recessed portion on a markformation area of a substrate; coating the recessed portion with apolymer layer containing a block copolymer; allowing the polymer layerin the recessed portions to form a self-assembly area; selectivelyremoving a portion of the self-assembly area; and forming a positioningmark by using the self-assembled area from which the portion thereof hasbeen removed.

According to a second aspect of the present teaching, there is provideda mark which is formed in a mark formation area of a substrate, the markcomprising:

a plurality of line-pattern areas formed periodically in a firstdirection; and at least one space-pattern area between the plurality ofline-pattern areas, wherein a first structure which is opticallyunresolvable is formed in the line-pattern areas, a second structurewhich is optically unresolvable is formed in the space-pattern area, anda periodic direction of the first structure is different from a periodicdirection of the second structure.

According to a third aspect of the present teaching, there is providedan exposure apparatus which illuminates a pattern with an exposure lightand exposes a substrate with the exposure light via the pattern and aprojection optical system, the exposure apparatus including: a markillumination system configured to illuminate a mark, formed in thesubstrate, with an illumination light of which polarization state iscontrollable; a detecting section configured to receive a light from themark and detect the mark; and a control system configured to control, ina case that a structure unresolvable by the illumination light isincluded in the mark, the polarization state of the illumination lightdepending on a periodic direction of the structure.

According to a fourth aspect of the present teaching, there is provideda method for producing a device including: forming in a substrate, analignment mark for alignment between layers of the substrate by usingthe mark forming method of the first aspect of the present teaching;performing the alignment by using the alignment mark and performingexposure for the substrate; and processing the exposed substrate.

According to a fifth aspect of the present teaching, there is provided amethod for producing a device, the method comprising: exposing aphotosensitive substrate by using the exposure apparatus of the thirdaspect; and processing the exposed photosensitive substrate.

According to the first aspect of the present teaching, it is possible toform a mark together with a circuit pattern when forming the circuitpattern using the self-assembly of the block copolymer.

Further, the mark of the second aspect can be formed by the mark formingmethod of the first aspect.

Furthermore, the exposure apparatus of the third aspect can detect amark formed by the mark forming method of the first aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block diagram depicting main parts or portions of a patternforming system used in an embodiment of the present teaching, FIG. 1B isa diagram depicting the overall configuration of an exposure apparatus100 depicted in FIG. 1A, and FIG. 1C is a diagram depicting a waferalignment system of FIG. 1B.

FIG. 2A is a plane view depicting a certain device layer of a wafer of afirst embodiment, and FIG. 2B is an enlarged plane view depicting one ofwafer marks and a part of a circuit pattern of FIG. 2A.

FIG. 3 is a flow chart indicating a pattern forming method of a firstembodiment.

FIGS. 4A, 4B, 4C, 4D, 4E, 4F, 4G and 4H are enlarged cross-sectionalviews each depicting a portion of a pattern of a wafer graduallychanging during a pattern forming step.

FIG. 5A is an enlarged plane view depicting a portion of a mark patternof a reticle, and FIG. 5B is an enlarged plane view depicting a “B”portion in FIG. 5A.

FIG. 6A is an enlarged plane view depicting a portion of a resistpattern formed on a surface of a wafer, and FIGS. 6B and 6C are enlargedplane views depicting a pattern of the “B” portion in FIG. 6A indifferent production steps, respectively.

FIGS. 7A, 7B and 7C are enlarged plane views depicting the pattern ofthe “B” portion in FIG. 6A in different production steps, respectively.

FIG. 8 is an enlarged plane view depicting the configuration of a wafermark formed in the first embodiment.

FIG. 9A is an enlarged plane view depicting a part of a resist patternof a first modification, and FIG. 9B is an enlarge view depicting a mainportion of FIG. 9A.

FIG. 10A is an enlarged cross-sectional view depicting the structure ofa plurality of layers of a wafer of a second modification, FIG. 10B isan enlarged plane view depicting a resist mark for a wafer mark of afirst device layer of FIG. 10A, and FIG. 10C is an enlarged plane viewdepicting a resist mark for a wafer mark of a second device layer ofFIG. 10A.

FIG. 11A is an enlarged plane view depicting a resist mark for a wafermark of a third modification, FIG. 11B is an enlarged view depicting aself-assembled pattern in a space-pattern area in FIG. 11A, and FIG. 11Cis an enlarged view depicting a self-assembled pattern in a line-patternarea in FIG. 11A.

FIG. 12 is an enlarged plane view depicting one of wafer marks and apart of a circuit pattern according to a second embodiment.

FIG. 13A is an enlarged plane view depicting a resist mark for a wafermark, FIG. 13B is an enlarged view depicting a self-assembled pattern ina space-pattern area in FIG. 13A, FIG. 13C is an enlarged view depictinga self-assembled pattern in a line-pattern area. in FIG. 13A, and FIG.13D is an enlarged view depicting another example of a self-assembledpattern in the line-pattern area.

FIG. 14A is an enlarged plane view depicting a resist mark for a wafermark of a modification, and FIG. 14B is an enlarged view depicting aself-assembled pattern of a line-pattern area of FIG. 14A.

FIG. 15 is a flow chart indicating an example of steps for producing anelectronic device.

EMBODIMENTS First Embodiment

A preferred first embodiment of the present teaching will be explainedwith reference to FIGS. 1A to 8. At first, an explanation will be givenabout an example of a pattern forming system usable for forming acircuit pattern of an electronic device (micro device) such as asemiconductor element, etc., in the embodiment.

FIG. 1A depicts the main parts or portions of the pattern forming systemof the embodiment, and FIG. 1B depicts the overall configuration of anexposure apparatus 100 depicted in FIG. 1A and which is an exposureapparatus (projection exposure apparatus) of the scanning exposure typeconstructed of a scanning stepper (scanner). In FIG. 1A, the patternforming system includes the exposure apparatus 100, a coater/developer200 which performs coating or application of a photoresist (resist) as aphotosensitive material for a wafer (substrate) and which performs thedevelopment of the coated (applied) photoresist, a thin film formingapparatus 300, an etching apparatus 400 which performs the dry etchingand the wet etching for the wafer, a polymer processing apparatus 500which performs processing of a polymer containing a block copolymer(BPC) to be described later on, an annealing apparatus 600, a transportsystem 700 which performs the transport of the wafer among theapparatuses, a host computer (not depicted in the drawings), and thelike.

The block copolymer used in the present teaching is a polymer includingnot less than two monomers each of which is present as a block unit, ora polymer derived from these monomers. Each of the blocks of themonomers includes a repeated sequence of the monomers. As the blockcopolymer, it is allowable to use any polymer such as diblock copolymer,triblock copolymer, or the like. Among these copolymers, the diblockcopolymer has blocks of two different monomers. The diblock copolymercan be abbreviated, for example, as “A-b-B”, wherein “A” represents apolymer of a first block, “B” represents a polymer of a second block,and “-b-” indicates that it is a diblock copolymer having the A blockand the B block. For example, “PS-b-PMMA” represents a diblock copolymerof polystyrene (PS) and polymethyl methacrylate (PMMA). In addition to achain block copolymer, it is allowable to use block copolymers havingother structures including, for example, a star copolymer, a branchedcopolymer, a hyper-branched copolymer, or graft copolymer, etc., as theblock copolymer of the present teaching.

Further, in the block copolymer, there is such a tendency that therespective blocks (monomers) constructing the block copolymer assembletogether to form individual micro phase-separated domains referred toalso as “micro domains” or simply as “domains”(tendency to undergo phaseseparation). The phase separation is a kind of the self-assembly(self-organization). The spacing distance between different domains andthe form thereof depend on the interaction between the different blocksin the block copolymer, the volume fraction and number of the differentblocks. The domains of the block copolymer can be formed, for example,as a result of annealing. The heating or baking which is a part of theannealing is a general process for raising the temperatures of asubstrate and of a coating layer (thin film layer) provided on thesubstrate to be higher than the ambient temperature. The annealing caninclude thermal annealing, thermal gradient annealing, solvent vaporannealing or other annealing methods. The thermal annealing is referredto as heat curing (thermal curing) in some cases, and used to induce thephase separation. The thermal annealing can be used also as a processfor reducing or removing any defect inside a layer of lateral microphase-separated domains. The annealing generally includes a process forperform heating at a temperature higher than the glass-transitiontemperature of the block copolymer for a certain period of time (forexample, several minutes to several days).

Further, in the embodiment, the directed self-assembly (DSA) is appliedto a polymer containing a block copolymer so as to allow the polymercontaining the block copolymer to form domains of nano-scale order whichare segmented in a suitable shape for the formation of a circuit patternand/or an alignment mark of a semiconductor device. The directedself-assembly is a technique in which a pattern of resist (resistpattern) formed, for example, in a lithography step is used as apre-pattern or guide pattern, and the arrangement of domains of theblock copolymer is controlled based on a spatial arrangement(topographic structure) defined by the pre-pattern or guide pattern. Asa method of generating or causing the directed self-assembly, it ispossible to use, for example, the grapho-epitaxy process which uses athree-dimensional pre-pattern or guide pattern. However, it is alsopossible to use the chemo-epitaxy process wherein a planar pre-patternor guide pattern is provided on a base layer.

In FIG. 1B, the exposure apparatus 100 is provided with an illuminationsystem 10; a reticle stage RST which holds a reticle R (mask)illuminated with illumination light or illumination light beam for theexposure (exposure light) IL from the illumination system 10; aprojection unit PU including a projection optical system PL whichprojects the illumination light IL allowed to exit (exiting) from thereticle R onto a surface of a wafer W (substrate); a wafer stage WSTwhich holds the wafer W; and a main controller 38 (see FIG. 1C)constructed of a computer controlling the entire operations of theexposure apparatus. In the following, an explanation will be given inFIG. 1B with the Z-axis being taken in parallel to an optical axis AX ofthe projection optical system PL, the Y axis being taken along adirection in which the reticle R and the wafer W are scanned relative toeach other in a plane perpendicular to the Z axis (plane substantiallyparallel to a horizontal plane), the X-axis being taken along adirection orthogonal to the Z-axis and the Y-axis, and directions ofrotation (inclination) about the X axis, the Y axis, and the Z axisbeing designated as θx, θy, and θz directions respectively.

The illumination system 10 includes, as disclosed for example in thespecification of United States Patent Application Publication No. US2003/025890, etc., a light source which generates the illumination lightIL and an illumination optical system which illuminates the reticle Rwith the illumination light IL. The ArF excimer laser beam (wavelength:193 nm) is used as an example of the illumination light IL. It is alsopossible to use, as the illumination light IL, the KrF excimer laserbeam (wavelength: 248 nm), the high harmonic wave such as the YAG laseror the solid-state laser (for example, the semiconductor laser).

The illumination optical system includes: a polarization controllingoptical system; a light amount distribution forming optical system (adiffraction optical element or a spatial light modulator, etc.); anilluminance uniformizing optical system including an optical integrator(such as, fly-eye lens or rod integrator (inner-reflection integrator)),etc.; a reticle blind (a fixed or variable field stop) (all of the aboveare not depicted in the drawings); and the like. The illumination system10 illuminates a slit-shaped illumination area IAR which is disposed ona pattern surface (lower surface), of the reticle R, defined by thereticle blind and which is elongated in the X direction, with theillumination light IL in a predetermined polarization state at asubstantially uniform illuminance distribution, under an illuminationcondition such as the dipole illumination (including a so-called leafillumination in which the shape of a secondary light source is elongatedin a leaf-like shape in a non-periodic direction of the pattern),quadrupole illumination, annular (zonal) illumination, or a normalillumination, etc.

The reticle stage RST holds (retains) the reticle R thereon by thevacuum attraction etc. The reticle stage RST is placed on the uppersurface of an unillustrated reticle base (surface parallel to the XYplane) so that the reticle stage RST is movable in Y direction at aconstant speed and the positions of the reticle stage RST in the X and Ydirections and the rotational angle of the reticle stage RST in the θzdirection are adjustable. The position information of the reticle stageRST is always detected at a resolution of, for example, about 0.5 nm toabout 0.1 nm via a movement mirror 14 (or a mirror-finished side surfaceof the stage) by a reticle interferometer 18 including a multi-axislaser interferometer. A reticle stage driving system (not depicted inthe drawings) including a linear motor, etc. is controlled based on ameasured value by the reticle interferometer 18, to thereby control theposition and the velocity of the reticle stage RST.

Further, the projection unit PU arranged at a position below or underthe reticle stage RST is provided with a barrel 24, and the projectionoptical system PL including a plurality of optical elements which areheld in a predetermined positional relationship inside the barrel 24.The projection optical system PL is, for example, telecentric on theboth sides and has a predetermined projection magnification β (forexample, reduction magnification such as ¼, ⅕, etc.). An image of thecircuit pattern in the illumination area IAR of the reticle R is formed,via the projection optical system PL, in an exposure area IA (areaconjugated with the illumination area IAR) inside one shot area amongthe shot areas of the wafer W by the illumination light IL allowed topass through the reticle R. The wafer W (semiconductor wafer) as thesubstrate in the embodiment includes, for example, a substrateconstructed of a disk-shaped base member having a diameter in a range ofabout 200 mm to about 450 mm and composed of, for example, silicon orSOI (silicon on insulator) etc., wherein a thin film for patternformation (oxide film, metal film, polysilicon film, etc.) is formed ona surface of the base member. Further, a photoresist is applied (coated)on a surface of the wafer as an object to be exposed (exposure target)to provide a predetermined thickness (for example, about several tens ofnm to about 200 nm).

Furthermore, for the purpose of performing the exposure to which theliquid immersion method is applied, the exposure apparatus 100 isprovided with a nozzle unit 32, which constructs a part or portion of alocal liquid immersion device 30, so as to surround an lower end portionof the barrel 24 holding an end-portion lens 26 which is included in theplurality of optical elements constructing the projection optical systemPL and which is an optical element closest to the image plane side(closest to the wafer W side), the local liquid immersion device 30being a device to supply a liquid Lq between the end-portion lens 26 andthe wafer W. A supply port for the liquid Lq of the nozzle unit 32 isconnected to a liquid supply device (not depicted) via a supply flowpassage and a supply tube 34A. A recovery port for the liquid Lq of thenozzle unit 32 is connected to a liquid recovery device (not depicted)via a recovery flow passage and a recovery tube 34B. The detailedconfiguration of the local liquid immersion device 30 is disclosed, forexample, in the specification of United States Patent ApplicationPublication No. US 2007/242247.

Moreover, the wafer stage WST is placed on an upper surface 12 a, of abase plate 12, which is parallel to the XY plane such that the waferstage WST is movable in the X and Y directions. The wafer stage WSTincludes a body 20 of the wafer stage (stage body 20); a wafer table WTBarranged on the upper surface of the stage body 20; and a Z-levelingmechanism (not depicted in the drawing) which is provided inside thestage body 20 and which drives the wafer table WTB such that theposition in the Z direction (Z position) and the tilt angles in the θxand θy directions of the wafer table WTB (wafer W) relative to the stagebody 20 are changed. A wafer holder (not depicted), which holds thewafer W for example by the vacuum attraction, etc. on a suction surfaceapproximately parallel to the XY plane, is provided on the wafer tableWTB. A flat-shaped plate (water-repellent plate) 28, having a surfacewhich is subjected to the liquid-repellent treatment for the liquid Lq,is provided on a portion of the upper surface of the wafer table WTB,the portion surrounding the wafer holder (wafer W); the surface of thewater-repellent plate 28 is provided to be approximately flush with thesurface of the wafer W (wafer surface) placed on the wafer holder.Further, during the exposure, the Z-leveling mechanism of the waferstage WST is driven based on a measured value by, for example, anautofocus sensor of the oblique incident system (not depicted in thedrawings) so that the wafer surface is matched (focused on) the imageplane of the projection optical system PL during the exposure.

Furthermore, reflection surfaces are formed by performing mirror-finishfor end surfaces in the Y and X directions of the wafer table WTB,respectively. The position information (including at least the positionsin the X and Y directions and the rotational angle in the θz direction)of the wafer stage WST is measured at a resolution of, for example,about 0.5 nm to about 0.1 nm by projecting interferometer beams to thereflection surfaces, respectively (may be to a movement mirror) from amulti-axis laser interferometer constructing a wafer interferometer 16.A wafer stage driving system including a linear motor, etc. (notdepicted in the drawings) is controlled based on a measured value of themeasurement, to thereby control the position and the velocity of thewafer stage WST. Note that the position information of the wafer stageWST may be measured with a detection device of an encoder systemprovided with a scale of diffraction grating type and a detection head.

Moreover, the exposure apparatus 100 is provided with a wafer alignmentsystem ALS which measures the position of a predetermined wafer mark(alignment mark) of the wafer W, and a spatial image measuring system(not depicted in the drawings) which is contained in the wafer stage WSTin order to measure the position of an image of an alignment mark of thereticle R formed by the projection optical system PL. The alignment isperformed for the reticle R and the respective shot areas of the wafer Wby using the spatial image measuring system (reticle alignment system)and the wafer alignment system ALS.

As depicted in FIG. 1C, the wafer alignment system ALS has: a markillumination system 36A which illuminates a mark to be detected (targetmark) with, for example, a non-polarized detection light in a relativelybroad range from the visible range to the near infrared range; adetection system 36B which collects a reflected light from the targetmark and forms an enlarged image of the target mark and which takes theenlarged image; a polarizing plate 36C which is capable of setting thepolarization state of the detection light to be irradiated onto thetarget mark to a linearly polarized light; a driving section 36D whichcan insert/retract the polarization plate 36C to/from the optical pathof the detection light and which can control the angle of thepolarization plate 36C in a range of 0 degrees to 180 degrees; and asignal processing section 39 which detects the position of the targetmark based on an imaging signal supplied from the detection system 36B.

The mark illumination system 36A has: a light guide 37 a which transmits(guides), for example, a light from a light source (not depicted in thedrawings); a condenser lens 37 b which shapes the detection light exitedfrom the light guide 37 a into a parallel light beam; a half mirror 37 cwhich reflects the detection light toward the target mark; and a firstobjective lens 37 d which focuses the detection light to an observationarea including the target mark. The detection section 36B has the firstobjective lens 37 d and a second objective lens 37 e which collect thereflected light from the target mark and form an image of the targetmark, the half minor 37 c arranged between the first and secondobjective lenses 37 d and 37 e, and a two-dimensional imaging element 37f of the CCD or CMOS type which takes an image of the target mark. In acase that the detection light is set to be a linearly polarized light ina direction according to the structure, etc. of the target mark, thedriving section 36D arranges the polarizing plate 36C, as an example,between the condenser lens 37 b and the half mirror 37 c under thecontrol of the main controller 38, and further controls the rotationalangle of the polarization plate 36C.

In FIG. 1B, when performing exposure of the wafer W, a shot area of thewafer W as the exposure target is moved beside the exposure area IA bythe movement (step movement) of the wafer stage WST in the X directionand the Y direction. Further, the liquid Lq is supplied from the localliquid immersion device 30 to a space between the projection opticalsystem PL and the wafer W. An image of a part of the pattern of thereticle R, which is formed by the projection optical system PL, isprojected onto a certain shot area among the shot areas of the wafer W,while the reticle R and the wafer W are moved synchronously in the Ydirection via the reticle stage RST and the wafer stage WST. By doingso, the certain shot area is subjected to the scanning exposure with theimage of the pattern of the reticle R. The step movement and thescanning exposure are repeated, and thus each of the shot areas of thewafer W is exposed with the image of the pattern of the reticle R in thestep-and-scan manner and the liquid immersion manner.

Next, a pattern for device (device pattern) as an object to be produced(production target) in the embodiment is, as an example, a circuitpattern for a gate cell of a static RAM (SRAM) as a semiconductorelement. The circuit pattern is formed by using the directedself-assembly (DSA) of a polymer containing a block copolymer. Further,in the embodiment, a wafer mark as an alignment mark for positioning oralignment is also formed in a device layer of a wafer W in which thedevice pattern is formed.

FIG. 2A depicts a wafer W in which the device pattern and the wafer markare formed. In FIG. 2A, a large number of shot areas SA (device patternformation areas) are provided on the surface of the wafer W in a statethat scribe line areas SL (mark formation areas) having predeterminedwidths are intervened between the shot areas SA in the X and Ydirections; a device pattern DP1 is formed inside each of the shot areasSA, and a wafer mark WM is formed in each of the scribe line areas SLprovided adjacent to one of the shot areas SA.

As depicted in FIG. 2B which is an enlarged view of portion B in FIG.2A, the device pattern DP1 includes a line-and-space pattern(hereinafter referred to as “L & S pattern”) 40X in which a plurality ofline patterns 40Xa extending in the Y direction are arranged in the Xdirection substantially at a period (pitch) px1 and a L & S pattern 40Yin which a plurality of line patterns extending in the X direction arearranged in the Y direction substantially at a period py1. The linepattern 40Xa, etc., are each formed, for example, of a metal, and theline width thereof is about not more than ½ times (half) the period px1,etc. As an example, the period px1 is substantially same as the periodpy1, and the period px1, etc., are each about one severalth of theminutest period (hereinafter referred to as “period pmin”) which can beobtained in a process in which the liquid immersion lithography using awavelength of 193 nm and, for example, a so-called double patterningprocess are combined. The value half (the value ½ times) the period px1is smaller than, for example, about 22 nm. In a case of forming the L &S patterns 40X and 40Y having such a minute period, a linear domain isformed in each of different blocks when the polymer containing the blockcopolymer is allowed to undergo the directed self-assembly.

Further, the wafer mark WM in each of the scribe line areas SL includesa X-axis wafer mark 44X in which a line-pattern area 44Xa and aspace-pattern area 44Xb each elongated in the Y direction and havingsubstantially same widths in the X direction are arranged in the Xdirection at a period p1, and Y-axis wafer marks 44YA, 44YB which aredisposed on two locations, and in each of which a line-pattern area 44Yaand a space-pattern area 44Yb each elongated in the X direction andhaving substantially same widths in the Y direction are arranged in theY direction at a period p2. The wafer marks 44YA and 44YB are arrangedto sandwich the wafer mark 44X therebetween in the direction. As anexample, the periods p1 and p2 are identical, and the period p1 isseveral times to several ten times the resolution limit (period) in theliquid immersion lithography having the wavelength of 193 nm.

Further, the line-pattern areas 44Xa, 44Ya and the space-pattern areas44Xb, 44Yb may be areas different in the reflectivity with respect to adetection light in case of performing detection with the wafer alignmentsystem ALS depicted in FIG. 1B. In this case, the resolution limit ofthe wafer alignment system ALS (the limit of optical detectionperformable by the wafer alignment system ALS) is expressed as λa/(2NA), using the wavelength λa of the detection light of the waferalignment system ALS and the numerical aperture NA of an objectiveoptical system. Furthermore, for detecting the wafer marks 44X, 44YA and44YB by the wafer alignment system ALS, it is required that the valuecorresponding to ½ of the period p1 of the wafer mark 44X is not lessthan the resolution limit of the wafer alignment system ALS, and thecondition under which the wafer marks 44X, 44YA and 44YB can be detectedby the wafer alignment system ALS is as follows:p1/2≥λa/(2NA)   (1)

As an example, provided that the wavelength λa is 600 nm, the numericalaperture NA is 0.9, then the period p1 may be about not less than 670nm. In the embodiment, since the directed self-assembly by which lineardomains are formed during formation of the device pattern DP1 isapplied, it is necessary to take into the consideration the fact thatthe linear domains are formed by the directed self-assembly of the blockcopolymer also during the formation of the wafer mark 44X, etc.

In the following, an explanation will be given about an example of apattern forming method for forming the wafer marks 44X and 44YB depictedin FIG. 2B by using the pattern forming system of the embodiment, withreference to a flow chart indicated in FIG. 3. Note that the devicepattern DP1 and the wafer mark 44YA are also formed together with thewafer marks 44X and 44YB. As an example, as depicted in FIG. 4A, asurface portion of a base member 50, of the wafer W, formed for exampleof silicon is a first device layer DL1 in which the wafer mark anddevice pattern are to be formed.

At first, in Step 102 of FIG. 3, the thin film forming apparatus 300 isused to form a hard mask layer 52 such as an oxide film or a nitridefilm on the surface of the device layer DL1 of the wafer W. Further, itis preferred to form a neutral layer (not depicted in the drawings) onthe hard mask layer 52 so that a polymer layer containing a blockcopolymer (to be described later on) has affinity with the hard masklayer 52 (is easily attachable to the hard mask layer 52). Further, thecoater/developer 200 is used so as to perform coating on the hard masklayer 52 or the neutral layer with, for example, a positive resist layer54 (see FIG. 4A). Note that it is allowable to use a bottomanti-reflection coating (BARC) as the hard mask layer 52. Further, theillumination condition of the exposure apparatus 100 is set, forexample, to the quadrupole illumination so that the minutest pattern canbe exposed in the X and Y directions, and the wafer W is loaded onto theexposure apparatus 100 (Step 104). Then, each of the shot areas SA ofthe wafer W is exposed with an image of the device pattern (devicepattern image; not depicted in the drawings) of the reticle R1 by theliquid immersion method. At the same time as the exposure is performedfor each of the shot areas SA, the scribe line area SL provided adjacentto each of the shot areas SA is exposed with an image 46XP, etc. of thepattern of the wafer mark (wafer mark pattern image 46XP, etc.) of thereticle R1 (Step 106). The wafer for which the exposure has beenperformed is unloaded from the exposure apparatus 100, and the resist isdeveloped at the coater/developer 200 so as to form a resist pattern 54A(see FIG. 4B) thereon. Afterwards, the slimming and resist curingprocessing are performed for the resist pattern 54A (Step 108). Notethat during the exposure of the pattern image of the reticle R1, it isalso possible to adjust the exposure amount to be great so that the linewidth of the resist pattern becomes narrow. In such a case, the slimmingcan be omitted.

As depicted in FIG. 5A, a pattern area corresponding to each of thescribe line areas SL of the reticle R1 is formed with the X-axis markpattern 46X and the Y-axis mark pattern 46YB that are the original ofthe wafer mark. The mark pattern 46X and the mark pattern 46YB areconstructed by arranging a line area 46Xa corresponding to theline-pattern area 44Xa of FIG. 2B and a line area 46Ya corresponding tothe line-pattern area 44Ya of FIG. 2B in the X direction and the Ydirection, respectively and by arranging a space area 46Xb correspondingto the space-pattern area 44Xb of FIG. 2B and a space area 46Ybcorresponding to the space-pattern area 44Yb of FIG. 2B in the Xdirection and the Y direction, respectively, at a period p1/β and aperiod p2/β (β is the projection magnification). The width of the lineareas 46Xa and 46Ya and the width of the space areas 46Xb and 46Yb aresubstantially same. For the convenience of the following explanation, animage of the reticle pattern by the projection optical system PL is anerected image.

A plurality of line patterns 48Y is formed in each of the line areas46Xa and 46Ya. The line patterns 48Y are each formed of alight-shielding film elongated in the X direction while having alight-transparent portion as the background thereof, and are arranged inthe Y direction at a period p4/β (see FIG. 5B which is an enlarged viewof a “B” portion of FIG. 5A). A plurality of line patterns 48X is formedin each of the space areas 46Xb and 46Yb (here, the areas surroundingthe line areas 46Xa and 46Ya, respectively). The line patterns 48X areeach formed of a light-shielding film elongated in the Y direction andare arranged in the X direction at a period p3/β (see FIG. 5B). Asdepicted in FIG. 5B, end portions in the longitudinal direction of theline patterns 48Y in the line area 46Xa are connected to an edge portionin the width direction of one line pattern 48X, among the line patterns48X, which is located at an end portion of the space area 46Xb.

The line width of the line pattern 48X is ½ times the period p3/βcorresponding thereto and the line width of the line pattern 48Y is ½times the period p4/β corresponding thereto. In the embodiment, theperiod p4/β is same as the period p3/β; and the period p3/β issubstantially same as the resolution limit on the object plane side ofthe projection optical system PL of the exposure apparatus 100(resolution limit of the liquid immersion lithography using thewavelength of 193 nm). It is allowable, however, that the period p3/β isabout slightly greater than the resolution limit. Accordingly, theimages 46XP, etc. of the mark patterns 46X and 46YB (combination of theline patterns 48X and the line patterns 48Y) of the reticle R1 areexposed to the scribe line area SL of the wafer W, by the exposureapparatus 100 with high precision.

FIG. 6A depicts an X-axis resist mark RPX and an Y-axis resist mark RPYBeach of which is composed of a resist pattern that is formed on the hardmask layer 52 of the wafer W after the exposure of the image of the markpatterns 46X and 46YB of the reticle R1 of FIG. 5A to the resist layer54, the development and the slimming therefor. In FIG. 6A the resistmark RPX is constructed by arranging line-group area RPXa correspondingto the line area 46Xa of the reticle R1 of FIG. 5A and space area RPXbcorresponding to the space area 46Xb of the reticle R1 of FIG. 5A in theX direction at the period p1, and the resist mark RPYB is constructed byarranging line-group area RPYa corresponding to the line area 46Ya ofthe reticle R1 of FIG. 5A and space area RPYb corresponding to the spacearea 46Yb of the reticle R1 of FIG. 5A in Y direction at the period p2.Further, FIG. 6B is an enlarged view depicting a “B” portion in FIG. 6A,and FIG. 6C and FIGS. 7A to 7C are each an enlarged view depicting aportion corresponding to the “B” portion in FIG. 6A.

A plurality of linear patterns 54B is formed in each of the space areasRPXb and RPYb (here, the areas surrounding the line areas RPXa, RPYa,respectively). The linear patterns 54B (hereinafter referred to as the“guide patterns 54B”) are each elongated in the Y direction, and arearranged in the X direction at the period p3 (see FIG. 6B). A pluralityof linear patterns 54C is formed in each of the line areas RPXa andRPYa. The linear patterns 54C (hereinafter referred to as the “guidepatterns 54C”) are each elongated in the X direction, and are arrangedin the Y direction at the period p4 (here, the period p4 is same as theperiod p3). The line widths of the guide patterns 54B and 54C are each,for example, about one severalth to about one several tenths of theperiod p3 (here, a period converted score of the resolution limit of theliquid immersion lithography having the wavelength of 193 nm) (see FIG.4B). As depicted in FIG. 6B, end portions in the longitudinal directionof the guide patterns 54C in the line area RPXa are connected to an edgeportion in the width direction of one guide pattern 54B, among the guidepatterns 54B, which is located at an end portion of the space area RPXb.Owing to this configuration, the structures of the resist marks RPX andRPYB become resilient even after narrowing the line width of the resistpattern by the slimming, etc., thereby making it possible to suppressany collapse, etc. of the guide patterns 54B and 54C constructing theresist marks RPX and RPYB in a latter-stage processing or downstreamoperation. Note that FIGS. 4A to 4H are each a cross-sectional viewdepicting a potion corresponding to a portion along a line D-D in FIG.6B.

Then, in Step 110, the wafer W in which the resist marks RPX and RPYBdepicted in FIG. 6A have been formed is transported to the polymerprocessing apparatus 500, and a polymer layer 56 containing a blockcopolymer (BCP) is formed (applied) on the wafer W (the wafer W iscoated with the polymer layer 56 containing the BCP) by, for example,the spin coating so that the polymer layer 56 covers the resist marksRPX and RPYB and a resist pattern (not depicted) for forming the devicepattern on the wafer W. In the embodiment, as an example, diblockcopolymer (PS-b-PMMA) of polystyrene (PS) and polymethyl methacrylate(PMMA) is used as the block copolymer. Further, although the polymerlayer 56 is the block copolymer itself, the polymer layer 56 may containa solvent for increasing the coating property and/or an additive forfacilitating the self-assembly, etc. By the spin coating, the polymerlayer 56 is deposited in recessed portions 70A and 70B between theprotruded guide patterns 54B and 54C respectively, constructing theresist marks RPX and RPYB (see FIGS. 4B, 4C and 6C).

Then, the wafer W having the polymer layer 56 formed thereon istransported to the annealing apparatus 600, and annealing (for example,thermal annealing) is performed for the polymer layer 56 to therebyallow the polymer layer 56 to separate into two kinds of domains by thedirected self-assembly (DSA) (Step 112). By the directed self-assemblyin this process, the polymer layer 56 between the guide patterns 54Belongated in the Y direction undergoes the phase separation, as depictedin FIGS. 7A and 4D, into a lyophilic first domain 56A composed of linearPMMA (polymethyl methacrylate) elongated in the Y direction and aliquid-repellent second domain 56B composed of linear PS (polystyrene)elongated in the Y direction, in a state that the lyophilic first domain56A and the liquid-repellent second domain 56B are periodically arrangedin the X direction at a period p3 a. Since the guide pattern 54B (resistpattern) is lyophilic, the lyophilic domains 56A are formed each in aportion adjacent to the guide pattern 54B. The period p3 a is, forexample, about one severalth to about one tenth of the period p3 of theguide patterns 54B, and the widths in the X direction of the two kindsof domains 56A and 56B are substantially same with each other.

Further, the polymer layer 56 between the guide patterns 54C elongatedin the X direction undergoes the phase separation into a lyophilic thirddomain 56C composed of linear PMMA elongated in the X direction and aliquid-repellent fourth domain 56D composed of linear PS elongated inthe X direction, in a state that the lyophilic third domain 56C and theliquid-repellent fourth domain 56D are periodically arranged in the Ydirection at a period p4 a. In the embodiment, the period p4 in the Ydirection of the guide patterns 54C is same as the period p3 of theguide patterns 54B, and the period p4 a of the domains 56C and 56D aresubstantially same as the period p3 a of the domains 56A and 56B. Theperiods p3 a and p4 a are substantially same as the periods px1 and py1of the L & S patterns 40X and 40Y formed in the shot area SA depicted inFIG. 2B. In the embodiment, the polymer layer 56 separates into the twokinds of domains elongated along each of the elongated guide patterns54B and 54C. During the separation, a condition under which the polymerlayer 56 easily separates into the two kinds of elongated domains isused also regarding the annealing of the polymer layer 56 (wafer W).

Afterwards, the wafer W is transported to the etching apparatus 400 and,for example, oxygen plasma etching is performed for the wafer W so as toselectively remove the lyophilic first and third domains 56A and 56Camong the domains 56A to 56D formed in the wafer W, as depicted in FIGS.7B and 4E (Step 114). Further, etching is performed for the hard masklayer 52 of the wafer W, with the resist marks RPX and RPYB (guidepatterns 54B and 54C) and the liquid-repellent domains 56B and 56Dallowed to periodically remain as a mask, so as to form a plurality ofopenings 52 a in the hard mask layer 52 (see FIG. 4F), and the remainingresist and the domains 56B and 56D are removed (Step 116). Further, theetching is performed for the first device layer DL1 of the wafer W, viathe hard mask layer 52 in which the openings 52 a are formed, so as toform a plurality of recessed portions DL1 Xa elongated in the Ydirection in the first device layer DL1 at areas corresponding to theplurality of domains 56A, respectively and to form a plurality ofrecessed portions DL1 Ya elongated in the X direction in the firstdevice layer at areas corresponding to the plurality of domains 56C,respectively, as depicted in FIG. 4G (first half of Step 118). Then, thewafer W is transported to the thin film forming apparatus 300, and byembedding a metal (for example, copper) into the recessed portions DL1Xa and the recessed portions DL1 Ya of the device layer DL1 of the waferW, to thereby form line patterns 58X and 58Y elongated in the Ydirection and the X direction, respectively, as depicted in FIG. 4H(second half of Step 118). As depicted in FIG. 7C, the period in the Xdirection of the line patterns 58X is the period p3 a, and the period inthe Y direction of the line patterns 58Y is the period p4 a (here, theperiod p4 a is same as the period p3 a). The line width of each of theline patterns 58X and 58Y is a value substantially corresponding to ½ ofthe period p3 a.

By the steps as described above, as depicted in FIG. 8, an X-axis wafermark 44X, in which the line-pattern area 44Xa having the plurality ofmetallic line patterns 58X arranged therein in the X directionsubstantially at the period p3 a and the space-pattern area 44Xb havingthe plurality of metallic line patterns 58Y arranged therein in the Ydirection substantially at the period p4 a are periodically arranged inX direction at the period p1, is formed in the scribe line area SL ofthe device layer DL1 of the wafer W. Further, Y-axis wafer marks 44YA,44YB which are disposed on two locations are arranged in the Y directionso that the X-axis wafer mark 44X is sandwiched between the Y-axis wafermarks 44YA and 44YB in the Y direction; in each of the Y-axis wafermarks 44YA, 44YB, the line-pattern area 44Ya having the line patterns58X (shorter than those in the wafer mark 44X) arranged therein in the Xdirection substantially at the period p3 a and the space-pattern area44Yb having the line patterns 58Y (longer than those in the wafer mark44X) arranged therein in the Y direction substantially at the period p4a are periodically arranged at the period p2 (here, the period p2 issame as the period p1).

In the embodiment, provided that a period converted score of theresolution limit (size limit which can be optically detected by using adetection light from the visible range to the near-infrared range) ofthe wafer alignment system ALS provided with the exposure apparatus 100is “Re(det)” and a period converted score of the resolution limit of theliquid immersion lithography using the wavelength of 193 nm is“Re(exp)”, then the period p1 of the line-pattern area 44Xa and thespace-pattern area 44Xb of the wafer mark 44X, the resolution limitRe(det), the resolution limit Re(exp) and the period p3 a of the linepatterns 58X and 58Y constructing the line-pattern are 44Xa andspace-pattern area 44Xb have the following relationship:p1≥Re(det)>Re(exp)>p3a   (2)

Accordingly, the period p3 a of the line patterns 58X and 58Y is smallerthan the resolution limit Re(det) of the wafer alignment system ALS.Therefore, in a case that images of the wafer marks 44X, 44YA and 44YBof FIG. 8 are taken by the wafer alignment system ALS, individual imagesof the plurality of line patterns 58X and 58Y are not formed. In thiscase, when the polarization direction of the detection light is set, forexample, in the X or Y direction, the reflectivity is different betweenthe line-pattern area 44Xa and the space-pattern area 44Xb, thebrightness of the entire image of the line-pattern area 44Xa isdifferent from the brightness of the entire image of the space-patternarea 44Xb, and thus an image of the X-axis wafer mark 44X having theperiod p1 can be detected. Similarly, images of the Y-axis wafer marks44YA and 44YB having the period p2 (here, p2 equals to p1) can also bedetected. The information in the longitudinal direction of the linepatterns 58X and 58Y constructing the wafer marks 44X, 44YA and 44YB isstored to an exposure data file in a memory (storage device) of the maincontroller 38 of the exposure apparatus 100.

Further, concurrently with the formation of the wafer marks 44X, 44YAand 44YB of FIG. 8, the L & S patterns 40X and 40Y depicted in FIG. 2Bare formed in each of the shot areas SA of the wafer W, by using thedirected self-assembly of the polymer layer containing the blockcopolymer in a similar manner as in the case for forming the wafermarks.

Then, in a case that a second device layer is formed on the device layerDL1 of the wafer W, a thin film is formed on the device layer DL1 of thewafer W, and coating is performed with a resist (Step 120). Afterwards,the reticle R2 is loaded onto the reticle stage RST of the exposureapparatus 100, and the wafer W is loaded onto the wafer stage WST (Step122). Further, the angle of the polarization plate 36C of the waferalignment system ALS of the exposure apparatus 100 is set so that thedetection light from the wafer alignment system ALS becomes, forexample, a linearly polarized light in the Y direction (may be in the Xdirection) with respect to the wafer mark 44X in FIG. 8 (Step 124).Then, the wafer alignment system ALS is used to thereby detect thepositions of the wafer marks WM (44X, 44YA, 44YB) provided adjacent to apredetermined plurality of shot areas SA of the wafer W of FIG. 2A, andthe alignment of the wafer W is performed by using the result of thedetection (Step 126).

Further, by exposing each of the shot areas SA of the wafer W with animage of a pattern of a reticle R2 for the second device layer (Step128), by performing: the development for the resist (Step 130) and byperforming a pattern formation such as the etching, etc., the pattern ofthe second device layer is formed (Step 132).

According to the pattern forming method of the embodiment as describedabove, the directed self-assembly of the polymer layer containing theblock copolymer is used so as to form the L & S patterns 40X and 40Y,each having the periodic structure more minute than the resolution limitof the liquid immersion lithography, in each of the shot areas SA of thewafer W, while forming the wafer mark 44X, etc., each having a periodicstructure more minute than the resolution limit of the liquid immersionlithography and a periodic structure same as or coarser than the sizelimit detectable by the wafer alignment system ALS, in each of thescribe line area SL. Further, in the wafer mark 44, etc., the periodicdirections of the minute structures in the line-pattern area 44Xa andthe space-pattern area 44Xb are orthogonal to each other. Accordingly,by using this difference in the structure, the positions of the wafermark 44X, etc., can be detected by the wafer alignment system ALS of theexposure apparatus 100 with high precision.

The effect, etc. of the embodiment are as follows. The mark formingmethod by the pattern forming system of the embodiment includes: Step106 of exposing the scribe line area SL of the wafer W with the imagesof the mark patterns 46X and 46YB; Step 108 of forming the resist marksRPX and RPYB including the recessed portions 70A and 70B, respectively,on the scribe line area SL based on the images of the mark patterns 46Xand 46YB; Step 110 of performing coating for the areas, of the wafer W,at which the recessed portions 70A and 70B of the resist marks RPX andRPYB are formed, with the polymer layer 56 containing the blockcopolymer; Step 112 of performing annealing for the polymer layer 56 soas to allow the polymer layer 56 to form the self-assembly area (thelyophilic domains 56A, 56C, and the liquid-repellent areas 56B, 56D);Step 114 of selectively removing a portion (domains 56A and 56C) of theself-assembly area by the plasma etching; and Steps 116 and 118 offorming the wafer marks 44X, 44YA and 44YB on the wafer W by using theself-assembly area from which the portion of the self-assembly area hasbeen selectively removed.

According to the mark formation method, when forming the circuit patternby using the self-assembly of the polymer layer 56 containing the blockcopolymer, it is possible to form the wafer marks 44X, 44YA and 44YBeach having the periodic structure more minute than the resolution limitof the liquid immersion lithography and the periodic structure same asor coarser than the size limit detectable by the wafer alignment systemALS, together with the formation of the circuit pattern.

Further, the wafer mark 44X for alignment of the embodiment includes:the plurality of line-pattern areas 44Xa formed periodically in the Xdirection; and at least one space-pattern area 44Xb formed between theline pattern areas 44Xa; wherein the plurality of line patterns 58X(first structure) having the period smaller than the resolution limit ofthe wafer alignment system ALS (structure which is opticallyunresolvable by the wafer alignment system ALS) is formed in each of theline pattern areas 44Xa, the plurality of line patterns 58Y (secondstructure) having a structure which is optically unresolvable is formedin each of the at least one space pattern area 44Xb, and the periodicdirection (X direction) of the line pattern 58X is orthogonal to theperiodic direction of the line pattern 58Y (Y direction). The wafer mark44X can be formed by the mark formation method of the embodiment.Further, by utilizing the configuration that the periodic direction ofthe line patterns 58X and the periodic direction of the line patterns58Y are different from each other, the image of the wafer mark 44X canbe formed by the wafer alignment system ALS of the exposure apparatus100, and the position of the wafer mark 44X can be detected with highprecision. By using the result of detection, the alignment for wafer Wcan be performed with high precision.

Although, in the wafer mark 44X of the embodiment, both of the areas44Xa and 44Xb have the structure which is optically unresolvable, it isallowable to provide a structure, which includes the line patterns 58Xor 58Y, etc., and which is optically unresolvable, on at least one ofthe line-pattern area 44Xa (line portion having the period which isoptically detectable) and the space-pattern area 44Xb (or the areasurrounding the line-pattern area 44Xa). In this case also, the wafermark can be formed by using the self-assembly of the block copolymer,and the wafer mark can be detected by allowing the reflectivity bedifferent between the line portion and an area adjacent to the lineportion.

Note that the above-described embodiment can be modified as follows.

In the embodiment, the period p3 of the X-axis guide pattern 54B and theperiod p4 of the Y-axis guide pattern 54C of the resist marks RPX andRPYB are same, as depicted in FIGS. 6A and 6B. As another configuration,in the resist marks RPX and RPYB, it is allowable to make the period p4of the Y-axis guide pattern 54C be greater than the period p3 of theX-axis guide pattern 54B, as depicted by a wafer W1 of a firstmodification in FIG. 9A. The first modification is applied in a casethat the minutest device pattern, among the device patterns formedtogether, is for example the X-axis L & S pattern 40X in FIG. 2B. In theabove situation, the exposure apparatus 100 uses such an illuminationcondition that the resolution in the X direction is minutest (forexample, the dipole illumination or leaf illumination wherein the lightamount is great at two areas on the pupil plane which are located apartin the X direction), in some cases. Since the resolution in the Xdirection is more minute than the resolution in the Y direction asdescribed above, by performing exposure with an image of a mark patternin which the period p4/β of the line pattern 48Y is made to be greaterthan the period p3/β of the line pattern 48X of FIG. 5B and byperforming the slimming, it is possible to form both of the X-axis guidepattern 54B and the Y-axis guide pattern 54C depicted in FIG. 9A, withhigh precision.

By forming the polymer layer 56 containing the block copolymer in therecessed portions 70A and 70C between the guide patterns 54B and 54C,respectively, and by allowing the polymer layer 56 to undergo thedirected self-assembly (to generate the directed self-assembly area) inthe first modification, the domains 56A and 56B are formed between theguide patterns 54B at the period p3 a in the X direction and the domains56C and 56D between the guide patterns 54C at the period p4 a in the Ydirection, and the period p4 a is different, for example, from theperiod p3 a, as depicted in FIG. 9B. Note that, however, the period p4 amay be same as the period p3 a. After the formation of the domains, awafer mark similar to the wafer mark of FIG. 8 can be formed by the samesteps as in the above-described embodiment.

Next, as indicated by a wafer W2 of a second modification of FIG. 10A,there is presumed a case that the minutest device pattern in a firstdevice layer DL1 of the wafer W2 is the X-axis L & S pattern 40X of FIG.2B, and that the minutest device pattern in a second device layer DL2,different from the first device layer DL1 of the wafer W2 (for example,a second device layer DL2 provided on an insulating layer 60A arrangedon the first device layer DL1) is the Y-axis L & S pattern 40Y of FIG.2B. Further, in this presumed case, a dipole illumination apart in the Xdirection is used when exposing the pattern of the first device layerDL1 so as to enhance the resolution in the X direction, and a dipoleillumination apart in the Y direction is used when exposing the patternof the second device layer DL2 so as to enhance the resolution in the Ydirection.

In this case, at the stage of resist pattern, a resist mark RPX isformed in the scribe line area (mark formation area) of the first devicelayer DL1, the resist mark RPX having an arrangement in which aplurality of line areas RPXa, each having a configuration in which guidepatterns 54B elongated in the V direction are periodically arranged inthe X direction, are arranged in the X direction in a state that spaceareas RPXb are intervened between the line areas RPXa, as depicted inFIG. 10B. An image of the pattern of a reticle based on which the guidepatterns 54B are formed is exposed by the dipole illumination in the Xdirection with high precision. In this modification, as an example, theresist film is allowed to remain in the space area RPXb and in the areasurrounding the line area RPXa; and a polymer layer containing the blockcopolymer is formed in recessed portions between the guide patterns 54Band the polymer layer is allowed to undergo the directed self-assembly(to generate the directed self-assembly area). By doing so, the domains56A and 56B are formed periodically in the X direction, as depicted inan enlarged view “B” of FIG. 10B. After this, the line patterns 58X areembedded (see FIG. 10A) in portions, of the device layer D1, located atpositions corresponding to the domains 56B, thereby forming the X-axiswafer mark 44X.

On the other hand, at the stage of resist pattern, resist marks RPYA,RPYB are formed in the scribe line area of the second device layer DL2,each of resist marks RPYA and RPYB having an arrangement in which aplurality of line areas RPYa, each having a configuration in which guidepatterns 54C elongated in the X direction are periodically arranged inthe Y direction, are arranged in the Y direction in a state that spaceareas RPYb are intervened between the line areas RPYa, as depicted inFIG. 10C. An image of the pattern of a reticle based on which the guidepatterns 54C are formed is exposed by the dipole illumination in the Ydirection with high precision. In this modification, as an example, theresist film is allowed to remain in the space area RPYb and in the areasurrounding the line area RPYa; and a polymer layer containing the blockcopolymer is formed in recessed portions between the guide patterns 54Cand the polymer layer is allowed to undergo the directed self-assembly(to generate the directed self-assembly area). By doing so, the domains56C and 56D are formed periodically in the Y direction, as depicted inan enlarged view “C” of FIG. 10(C). After this, the line patterns 58Yare embedded in portions, of the device layer DL2, located at positionscorresponding to the domains 56D (see FIG. 10A), thereby forming theY-axis wafer marks 44YA and 44YB. Afterwards, the X-axis wafer mark ofthe first device layer DL1 and the Y-axis wafer mark of the seconddevice layer DL2 are detected by the wafer alignment system ALS whenperforming the alignment for the wafer W2, thereby making it possible toperform the alignment in the X and Y directions for the wafer W2.

Next, as indicated by a water W3 of a third modification of FIG. 11A, itis allowable to form, at the stage of resist pattern, a resist mark RPXAin the scribe line area of a certain device layer of the wafer W3, theresist mark RPXA having a configuration wherein a plurality of lineareas RPXa each of which is formed of a wide recessed portion 70Dsurrounded by a frame-shaped projected pattern 54CA elongated in the Ydirection are arranged in the X direction in a state that space areasRPXb, each of which is composed of a plurality of guide patterns 54Barranged periodically in the X direction, are intervened between theline areas RPXa. In this case, the polymer layer containing the blockcopolymer is formed in recessed portions 70A between the guide patterns54B in the space area RPXb and in the wide recessed portion 70D of eachof the line areas RPXa, and the polymer layer containing the blockcopolymer is allowed to undergo the self-assembly. In this modification,between the guide patterns 54B of the space area RPXb, periodic domains56A and 56B extending in the Y direction are formed due to the strongdirectionality, as depicted in FIG. 11B. On the other hand, in therecessed portion 70D inside each of the line areas RPXa, theself-assembly is generated in a state that a lyophilic domain 56E and aliquid-repellent domain 56F are randomly combined as depicted in FIG.11C, since the directionality is weak in each of the line areas RPXa.

Afterwards, by performing processing similar to those in theabove-described embodiment, an X-axis wafer mark is formed in a statethat metallic line patterns are formed randomly in the line areas RPXaand that metallic line patterns elongated (extending) in the Y directionare periodically formed in the X direction in the space area RPXb. Inthis wafer mark also, the reflectivity of the detection light isdifferent between the space and line areas, and thus the wafer mark canbe detected by the wafer alignment system ALS.

Second Embodiment

An explanation will be given about a second embodiment, with referenceto FIGS. 12 to 13D. Also in the second embodiment, a device pattern anda wafer mark are formed in a certain device layer of the wafer by usingthe pattern forming system of FIG. 1A while employing the directedself-assembly (DSA) of the block copolymer (BCP). Although the shotarrangement of a wafer of the second embodiment is similar to the shotarrangement of the wafer W of FIG. 2A, the second embodiment forms adevice pattern DP2 in each of the shot areas SA, instead of forming thedevice pattern DP1.

FIG. 12 depicts the device pattern DP2 formed in each of the shot areasSA and the wafer marks 44X, 44YA and 44YB formed in each of the scribelines SL, of a certain device layer of a wafer (hereinafter referred toas “wafer W4”) of the second embodiment. The device pattern DP2 includesa hole array 42 constructed of a large number of minute holes (via orthrough holes) 42 a which are arranged in the X direction at a periodpx2 and arranged in the Y direction at a period py2. Note that the holes42 a is filled, for example, with a metal (for example, copper) in alatter-stage processing.

As an example, the periods px2 and py2 are substantially same, but theperiods px2 and py2 may be different from each other. The diameter ofthe hole 42 a is about not more than ½ times the period px2. As anexample, the periods px2 and py2 are each, for example, about oneseveralth of the minutest period “pmin” which can be obtained in aprocess in which the liquid immersion lithography using a wavelength of193 nm and, for example, a so-called double patterning process arecombined.

In the second embodiment, since the block copolymer undergoes theself-assembly so that a plurality of grid points arranged in the X and Ydirections are formed during formation of the device pattern DP2, theformation of wafer mark also employs the fact that the block copolymerundergoes the self-assembly such that a plurality of grind points areformed.

FIG. 13A depicts an resist mark RPXB for the X-axis wafer mark 44Xhaving the period p1 and formed in the scribe line area of the wafer W4.As an example, the resist mark RPXB has a configuration wherein a spacearea. RPXBb, formed of grid-shaped and projected guide patterns 54Ewhich are formed in the X and Y directions at a period p5, and a linearea RPXBa, formed of grid-shaped and projected guide patterns 54F whichare formed in the X and Y direction at a period p6 smaller than theperiod p5 (for example, the p6 being approximately ½ times the periodp5), are arranged in the X direction at the period p1. The period p6 isapproximately same as the resolution limit of the liquid immersionlithography using the wavelength of 193 nm. The thicknesses of the guidepatterns 54E and 54F are processed to be slim (small) so that thethicknesses of the guide patterns 54E and 54F become about one severalthto about one tenth of the periods p5 and p6, respectively, by theslimming of the resist pattern, etc.

In this embodiment, by forming a polymer layer containing the blockcopolymer in recessed portions 70E between the grid-shaped guidepatterns 54E in the space area and by allowing the polymer layer toundergo the directed self-assembly, as an example, minutecircular-shaped and lyophilic domains 62A are formed inside each of therecessed portions 70E as depicted in FIG. 13B such that the domains 62Aare arranged in a 3×3 matrix form in the X and Y directions at a periodp5 a; and that a neutral domain 62B composed of a lyophilic domaincontacting with the guide pattern 54E and a liquid-repellent domain isformed between each of the guide pattern 54E and domains 62Acorresponding thereto.

On the other hand, by forming the polymer layer containing the blockcopolymer in recessed portions 70F between the grid-shaped guidepatterns 54F in the line area and by allowing the polymer layer toundergo the directed self-assembly, as an example, the minutecircular-shaped and lyophilic domains 62A are formed inside each of therecessed portions 70F as depicted in FIG. 13C such that the domains 62Aare arranged in a 2×2 matrix form in the X and Y directions at a periodp6 a; and that the neutral domain 62B is formed between each of theguide patterns 54F and domains 62A corresponding thereto. In theembodiment, as an example, the period p5 a is ⅓ times the period p5, theperiod p6 a is ½ times the period p6, and the period p6 a is made to besmaller than the period p5 a, thereby making the density of the domains62A in the line area be greater than the density of the domains 62A inthe space area.

Then, in a similar manner as in the first embodiment, by selectivelyremoving the domains 62A, by performing etching for a hard mask layer(not depicted in the drawings) provided as a layer below the domains62A, with a pattern allowed to remain after the selective removal of thedomains 62A as a mask, and by further performing etching for a devicelayer (not depicted in the drawings) provided as a layer below the hardmask layer, a wafer mark in which portions corresponding to the domains62A becomes recessed portions is formed. Furthermore, for example, byembedding a metal into the recessed portions, a wafer mark including aspace pattern area in which portions corresponding to the domains 62A ofFIG. 13B are formed of the metal and a line pattern area in whichportions corresponding to the domains 62A of FIG. 13C are formed ofmetal is formed. In this wafer mark, the density is different betweenthe minute and circular-shaped metal pattern in the space pattern areaand the minute and circular-shaped metal pattern in the line patternarea, and thus the reflectivity of the detection light is differentbetween the space pattern areas and line pattern areas. Therefore, thewafer mark can be detected by the wafer alignment system ALS of theexposure apparatus 100.

Note that in this embodiment, the density of the domains 62A in thespace area may be made to be higher than the density of the domains 62Ain the line area.

Further, as a modification of this embodiment, it is allowable to makethe inside of the line area RPXBa be a wide recessed portion, withoutforming the grid-shaped guide patterns 54F therein. In such a case, inthe inside of the line area RPXBa, for example, lyophilic domains 56Eand liquid-repellent domains 56F are arranged randomly due to theself-assembly of the block copolymer, as depicted in FIG. 13D.Alternatively, circular domains are randomly arranged in some cases.Further, by selectively removing the domains 56E, a pattern composed ofrandom recessed portions (or random metal portions) is formed in theline area. In this case also, since the reflectively is differentbetween portions of the regularly arranged circular recessed portion (orregularly arranged metal portions) and portions of the randomly arrangedrecessed portion (or randomly arranged metal portions), the wafer markcan be detected by the alignment system ALS.

Next, as another modification of the embodiment, it is allowable to forma resist mark RPXC in which a line area RPXCa formed of a plurality ofguide patterns 54B arranged periodically in the X direction and spaceareas RPXCb having the entire surface thereof covered with a resist arearranged in the X direction as depicted in FIG. 14A. Further, the spaceareas RPXCb may be made as a base layer (for example, a metallic layer).In this case, the block copolymer is allowed to undergo the directedself-assembly in such a state that a large number of holes are firmed ina device pattern (not depicted in the drawings). Therefore, a polymerlayer containing the block copolymer is formed in recessed portions 70Abetween the guide patterns 54B of the line area RPXCa, and the polymerlayer containing the block copolymer is allowed to undergo the directedself-assembly. By doing so, as an example depicted in FIG. 14B, minutecircular-shaped lyophilic domains 62A are regularly formed in the X andY directions inside an intermediate domain 62B between the guidepatterns 54B. Afterwards, in a similar manner as in the above-describedexample, by selectively removing the domains 62A and by embedding, forexample, a metal in portions from which the domains 62A have beenselectively removed, there is formed a wafer mark having such a shapethat minute, circular-shaped metallic patterns are aligned in each ofthe line pattern areas and that any pattern is not present in each ofthe space pattern areas. Note that in this case, the line area RPXCa isnot limited to being formed of the above-described minute,circular-shaped lyophilic domain 62A, and may be formed of alinear-shaped lyophilic domain 62A and the intermediate domain 62B;alternatively, it is allowable to apply an aspect of forming the linearea RPXCa with a configuration wherein the lyophilic domain 56E and theliquid-repellent domain 56F are randomly arranged, as depicted in FIG.13D. This wafer mark having this configuration can also be detected bythe wafer alignment system ALS.

Next, in a case that a semiconductor device (electronic device) such asa SRAM is produced by using the pattern forming method of the respectiveembodiments described above, the semiconductor device is produced, asdepicted in FIG. 15, by performing a step 221 of designing the functionand the performance of the semiconductor device; a step 222 ofmanufacturing a mask (reticle) based on the designing step; a step 223of producing a substrate (or a base material for a wafer) for thesemiconductor device; a substrate-processing step 224; a step 225 ofassembling the device (including processing processes such as a dicingstep, a bonding step, and a packaging step); an inspection step 226; andthe like. Further, the substrate-processing step 224 includes thepattern forming method of the embodiments as described above, and thepattern forming method includes a step of exposing the substrate with apattern of the reticle by an exposure apparatus, a step of developingthe exposed substrate, a step of heating (curing) and etching thedeveloped substrate, etc.

In other words, the method for producing the device includes thesubstrate-processing step 224, and the substrate-processing step 224includes a step of forming the device pattern and the wafer mark on thesubstrate by using the pattern forming method of any one of therespective embodiments.

According to the method for producing the device, it is possible toproduce a semiconductor device including a circuit pattern finer (moreminute) than the resolution limit of the exposure apparatus, with highprecision by using the exposure apparatus.

Note that devices as the object to be produced in the respectiveembodiments may be any semiconductor device different from the SRAM,such as DRAM (dynamic random-access memory), CPU (central processingunit), IMP (digital signal processor), etc. Further, when producingelectronic devices (microdevices) different from the semiconductordevices, such as imaging elements, MEMS (MicroelectromechanicalSystems), etc., the pattern forming method of the respective embodimentsas described above is applicable.

Further, in the above-described embodiments, it is allowable to use adry-type exposure apparatus different from the exposure apparatus of theliquid immersion type. Furthermore, other than the exposure apparatususing the ultraviolet light as the exposure light, it is also allowableto use an EUV exposure apparatus employing an EUV light (ExtremeUltraviolet Light) of which wavelength is about several nm to aboutseveral tens of nm as the exposure light, or an electron beam-exposureapparatus employing an electron beam as the exposure light, etc.

Furthermore, in the above-described embodiments, diblock copolymercomposed of (Ps-b-PMMA) is used as the block copolymer. Other than this,substances usable as the block copolymer include, for example,poly(styrene-b-vinylpyridine), poly(styrene-b-butadiene),polystyrene-b-isoprene), poly(styrene-b-methacrylate),poly(styrene-b-aromatic alkenyl), poly(isoprene-b-ethylene oxide),poly(styrene-b-(ethylene-propylene)), poly(ethyleneoxide-b-caprolactonc), poly(butadiene-b-ethylene oxide),poly(styrene-b-t-butyl(meth)acrylate), poly(methylmethacrylate-b-t-butyl methacrylate), poly(ethylene oxide-b-propyleneoxide), poly(styrene-b-tetrahydrofuran),poly(styrene-b-isoprene-b-ethylene oxide),poly(styrene-b-dimethylsiloxane), or poly(methylmethacrylate-b-dimethylsiloxane); or diblock or triblock copolymers,etc., including a combination including at least one of theabove-described block copolymers; and the like. Further, it is alsopossible to use a random copolymer as the block copolymer.

It is preferred that the block copolymer has overall molecular weight orpolydispersity for making it possible to perform any further processing.

Further, coating of the polymer layer containing the block copolymer canbe performed also by a solvent casting method wherein the coating isperformed with a liquid in which the polymer layer is dissolved in asolvent, and then, for example, the solvent is allowed to volatilize. Inthis case, the usable solvent is changed depending on the components ofthe block copolymer, and in a case that additives are used, the usablesolvent is changed depending on the dissolving conditions of variouskinds of the additives. The exemplary casting solvents for thesecomponents and additives include propylene glycol monomethyl etheracetate (PGMEA), ethoxy ethyl propionate, anisole, ethyl lactate,2-heptanone, cyclohexanone, amyl acetate, γ-butyrolactone (GBL),toluene, etc.

Further, additives which can be added to the polymer layer containingthe block copolymer can be selected from the group including: anadditional polymer (including a homopolymer, a star polymer andcopolymer, a hyperbranched polymer, a block copolymer, a graftcopolymer, a hyper-branched copolymer, a random copolymer, across-linked polymer, and an inorganic material-containing polymer); asmall molecule; a nano-particle; a metallic compound; an inorganicmaterial-containing molecule; a surfactant; a photo acid generatingagent; a thermal acid generating agent; a basic quencher; a curingagent; a cross-linking agent; a chain extending agent; and a combinationincluding at least one of the above-described substances. Here, one orplurality of additives assocciate(s) together with the block copolymerto form one or plural portion(s) of the self-assembly domains.

Note that the present teaching is not limited to the embodimentsdescribed above, and may be embodied in other various forms orconfigurations within a scope without deviating from the gist oressential characteristics of the present teaching.

What is claimed is:
 1. A method for producing a device comprising:setting a mark formation area and a device production area differentfrom the mark formation area on a substrate; coating the mark formationarea and the device production area with a polymer layer containing ablock copolymer; allowing the polymer layer to form a self-assembledarea; selectively removing a portion of the self-assembled area; formingan alignment mark in the mark formation area by using the self-assembledarea from which the portion of the self-assembled area has been removed.2. The method for producing the device according to claim 1, wherein themark formation area includes a first area and a second area, and theforming of the alignment mark in the mark formation area by using theself-assembled area from which the portion of the self-assembled areahas been removed includes forming a first structure in the first areaand forming a second structure different from the first structure in thesecond area.
 3. The method for producing the device according to claim2, wherein the first structure includes a first periodic pattern havinga periodic direction in a first direction, and the second structureincludes a second periodic pattern having a periodic direction in asecond direction different from the first direction.
 4. The method forproducing the device according to claim 2, further comprising: forming afirst guide pattern in the first area of the mark formation area; andforming a second guide pattern in the second area of the mark formationarea.
 5. The method for producing the device according to claim 4,wherein the allowing of the polymer layer to form the self-assembledarea includes allowing the polymer layer in the first area to form theself-assembled area having a periodic direction in a first direction andallowing the polymer layer in the second area to form the self-assembledarea having a periodic direction in a second direction different fromthe first direction.
 6. The method for producing the device according toclaim 2, wherein the first structure includes a hole pattern array. 7.The method for producing the device according to claim 6, wherein thesecond structure includes a random pattern.
 8. The method for producingthe device according to claim 1, further comprising: detecting aposition of the substrate by using the alignment mark, and processingthe substrate of which position has been detected.
 9. The method forproducing the device according to claim 8, wherein the processing of thesubstrate includes exposing the substrate.
 10. A method for producing adevice comprising: setting a mark formation area including a first areaand a second area on a substrate; coating the mark formation area with apolymer layer containing a block copolymer; allowing the polymer layerto form a self-assembled area; selectively removing a portion of theself-assembled area; forming a first structure in the first area of themark formation area and forming a second structure different from thefirst structure in the second area of the mark formation area, by usingthe self-assembled area from which the portion of the self-assembledarea has been removed; and detecting a position of the substrate byusing at least one of the first and second structures.
 11. The methodfor producing the device according to claim 10, wherein the firststructure includes a first periodic pattern having a periodic directionin a first direction, and the second structure includes a secondperiodic pattern having a periodic direction in a second directiondifferent from the first direction.
 12. The method for producing thedevice according to claim 10, further comprising: forming a first guidepattern in the first area of the mark formation area; and forming asecond guide pattern in the second area of the mark formation area. 13.The method for producing the device according to claim 12, wherein theallowing of the polymer layer to form the self-assembled area includesallowing the polymer layer in the first area to form the self-assembledarea having a periodic direction in a first direction and allowing thepolymer layer in the second area to form the self-assembled area havinga periodic direction in a second direction different from the firstdirection.
 14. The method for producing the device according to claim10, wherein the first structure includes a hole pattern array.
 15. Themethod for producing the device according to claim 14, wherein thesecond structure includes a random pattern.
 16. The method for producingthe device according to claim 10, further comprising processing thesubstrate of which position has been detected.
 17. The method forproducing the device according to claim 16, wherein the processing ofthe substrate includes exposing the substrate.